1. Field of the Invention
The present invention relates to a device for improving the quality of the carburetted mixture which is delivered by a pneumatic injection system feeding a reciprocating internal combustion engine.
2. Description of the Prior Art
Such engines are usually supplied, either by a carburettor, or by direct or indirect injection of the liquid fuel. In the first case, the prior mixture of air and fuel takes place appreciably upstream of the intake ports of the cylinders, which causes inhomogeneities both in the distribution of the fuel in the air and in the distribution of the mixture between the cylinders. These imperfections are prejudicial to the efficiency of the engine, all the more so since mixture may be lost to the exhaust when the cylinder is scavenged by the mixture admitted, (in particular in two stroke engines). Finally, controlling the amount of fuel in the air becomes very delicate when the carburetion must be optimized with a view to saving energy and reducing pollutants.
Direct or indirect injection of the liquid fuel palliates the harmful effects of a poor distribution between cylinders and losses to the exhaust, and facilitates control of the fuel.
It has however, the drawback of creating inhomogeneities of the mixture in the cylinders, which may result in poor combustion, particularly at high speeds.
A third method is still little used or not used at all in reciprocating engines, namely pneumatic injection.
This process combines the advantages of direct or indirect liquid injection with those of carburetion. In fact, the fluid mixture introduced is already a partly prepared carburetted mixture, distribution thereof may be independent for each cylinder and determined so as to minimize the losses to the exhaust.
The prior art may be illustrated by the following French Pat. Nos.: FR-A- 563 174, FR-A-313 652, FR-A-1 037 550 and FR-A-669 767.
The proposed invention concerns the arrangement of a pneumatic injector using a nozzle for improving the air-injected fuel mixture.